Allow specification of destination directory when initializing a project

[mwvaughn]

The original behavior for abaco init was to create a new project in $PWD. This caused some minor degree of annoyance if the parent directory was already managed by Git, or if it was just inconvenient for this to be the location of the directory.

Enable specification of the base path to abaco init, checking that the designated path exists and failing with a CRITICAL error if not.

[mwvaughn]

This is resolved in 0cf51b8 which includes a -B option for abaco init

[mwvaughn]

Reopening to test